function [Ix,Iy,It] = ImageDerivatives(I1,I2)
    Ky = 0.25.*[-1 -1;1 1];
    Kx = 0.25.*[1 -1;1 -1];
    Kt = 0.25.*[1 1;1 1];
    
    Ix = conv2(I1,Kx,'same') + conv2(I2,Kx,'same');
    Iy = conv2(I1,Ky,'same') + conv2(I2,Ky,'same');
    It = conv2(I2,Kt,'same') - conv2(I1,Kt,'same');
    
end
